Fish carburetor

from Wikipedia, the free encyclopedia
This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.


The Fish carburetor goes back to an invention by the American John Robert Fish in the 1930s. JR Fish was not an engineer , more like a kind of "all-round inventor " with a great deal of knowledge about pressure differences and mechanics .

background

JR Fish first started looking at carburetors when he recognized their major problem. After a sharp corner with his Ford Model T , the engine died .

Conventional carburetors are very dependent on a correct float level . In sharp bends is in the extreme case, due to the centrifugal force , fuel in the nozzle is pressed or removed therefrom. Both have an effect on the engine running, in extreme cases the engine even dies completely and has to be restarted. Large V8 carburettors therefore had up to 4 float chambers around them to counteract this.

Conventional carburetors are based on the Venturi principle ; Incoming air is accelerated and pulls the fuel with it from the nozzle, which is atomized and finally fed to the combustion. Since gasoline is very sluggish in relation to air, a setting that tends to be too rich must be selected, especially at low engine speeds , as the fuel cannot be atomized correctly / efficiently. The mixture is usually artificially emaciated again by further venturis or jets . Poorly atomized fuel doesn't burn particularly well either.

development

Fish therefore experimented with various carburetors and came to the conclusion that a new development was necessary for his goals.

This offered several advantages:

  • Better combustion / mixture formation
  • Less consumption
  • More efficient
  • Relative independence from swimmer levels
  • Independence from atmospheric influences

Working principle

The Fish carburetor is not based on the Venturi principle, but on the principle of the pressure difference .

construction

It works without jets, carburetor needles or jets in the conventional way. Instead, it has a series of holes in a hollow throttle shaft. These are slightly larger on the inlet side than on the engine side.

The throttle itself is just clamped onto the shaft. It ends directly in the carburetor's float chamber.

This is also rather unconventional. It is divided into two compartments by a brass plate . On the outside there is a normal float , on the inside, on the carburetor side, there is also a hollow brass arm , which is firmly connected to the throttle valve shaft. It just fits between the partition and the housing. When the throttle is moved, it swings through the smaller float chamber. At the same time it serves as an acceleration pump . The already mentioned brass plate is provided with two holes. The hole on the "full throttle" side is provided with a check valve. If you step sharply on the accelerator pedal , the arm snaps in the direction of the non-return valve, which closes and the gasoline is thus pressurized . The only way out is the hollow arm through which the gasoline is injected into the carburetor.

This pump works so efficiently that the pressure has to be reduced. This happens through the so-called meeting groove , a deepening groove through which some of the gasoline can flow past the arm. Otherwise the engine would "drown". At the same time, it ensures that gasoline is not necessarily injected when the throttle is operated normally.

The most important regulation instance, however, is a screw in the hollow throttle valve shaft, which regulates the total amount of gasoline that is allowed to enter the carburetor.

function

In idle and part-load range , the intake air flows through the holes in the throttle shaft and mixes with the gasoline. The mixture emerges on the underside and is burned .

The air-fuel ratio is influenced by the prevailing negative pressure and the angle between the throttle valve and the shaft. Turning the throttle valve on the throttle valve shaft does not change the (relative) amount of fuel in relation to the air, but the (relative) amount of air to the fuel.

Towards full throttle, respectively vertically standing throttle all more holes to outlet orifices. At a throttle valve angle of 90 °, the rather massive throttle valve forms a kind of inverted Venturi shape . All holes now function as a nozzle .

Due to this structure, the carburetor is almost constantly spraying itself automatically. Ambient pressures do not have such a noticeable influence on the tuning as with other carburetors. Due to the many holes in the throttle valve shaft, respectively. Nozzles, the Fish carburetor atomizes the fuel much finer. This ensures lower consumption and improved combustion.

When idling, there is a correction valve that also makes the idle mixture leaner.

Pro Contra

The big disadvantage of the Fish carburetor is that it needs the highest possible vacuum or negative pressure in order to function properly. Small-volume engines should therefore be driven with the smallest possible carburetor. It does not meet modern emissions regulations , due to the powerful acceleration pump.

In the case of small-volume engines (e.g. mini ), it is advisable to increase the compression in order to ensure optimal function. Otherwise the carburetor can even lead to higher consumption, as it cannot work properly.

history

In the America of the 1930s, John Robert Fish initially sold his carburetor very successfully. He soon moved with his company to Florida , where he made the carburetor popular in motorsport . Especially in the races on Daytona International Speedway , JR Fish's racing cars achieved considerable success. But here too he was boycotted. Close to financial ruin a friend, a smaller version of the carburetor persuaded him to manufacture (previously it was only for large-volume V8 engines designed have been) to the early 1950s, the growing market for VW Beetles to operate.

But that only saved the company for a short time and finally all rights were first transferred to the Canadian Eric Liebman. When this could no longer meet the needs in Europe, Liebman transferred the rights to Bob Henderson from England . He manufactured the carburetor in the small version for VW Beetles, Mini Cooper and other European vehicles under the name Minnow-Fish .

Later, in the 1960s, the rights went to Leonard Reece, who improved the carburetor again. Among other things, it now had a freely rotating float chamber and could therefore be attached to a vehicle in all positions and positions. That was a great competitive advantage, and so the "Reece Fish" carburetor became one of the most popular accessory carburetors in the 1960s and 1970s, not least because of its low price.

Web links